Introdution Plagioclase, pl, is an important constituent of planetary surfaces, e.g. Moon and Mercury. Spectrometer detected crystalline pl on the lunar surface [1-2], with composition of ~An90 and variable FeO content. New data from XRS and GRS on the Hermean surface show contents of Na [3] that are compatible with low-An pl. Natural and synthetic plagioclase spectroscopy Fig. 1 Natural (left) and synthetic (right) spectra of pl. Visible and near-infrared reflectance (VNIR) spectroscopy is the most used technique to map the surface of Solar System bodies. Pl, often considered a spectrally neutral phase, shows a clear absorption at ca. 1.25 ?m, even for very low FeO contents (Fig. 1, left); furthermore, an increase of this component, causes an increase of the depth of the absorption band, while its position moves to the IR region. We synthesised pl with different An and FeO content, in order to investigate how these parameters control the absorption band in the VNIR region. Plagioclase An90 was synthesized from oxides and carbonate at logfO2= -9; the mixture was first heated at 1600 °C for 15 minutes, quenched and then re-heated at 1400 °C for 24 hours. XRD and EPMA confirmed the presence of a crystalline phase, as well as its compositional homogeneity. As an example, a spectrum of a synthetic pl (An90) containing 0.5 wt% FeO is reported in Fig. 1, right. Conclusion and future works The synthesys of different pl will allow to create a VNIR spectra database wich will be invaluable to better constrain the composition of the crust of Solar System bodies. [1] Ohtake M. et al. (2009) Nature, 461, 236-241. [2] Cheek L.C. et al. (2012) Second Conference on the Lunar Highlands Crust, Abstract #9022. [3] Evans et al. (2013) LPSC XLIV, Abstract #2033.
Natural and synthetic plagioclases for the interpretation of planetary surfaces
Orlando A;
2013
Abstract
Introdution Plagioclase, pl, is an important constituent of planetary surfaces, e.g. Moon and Mercury. Spectrometer detected crystalline pl on the lunar surface [1-2], with composition of ~An90 and variable FeO content. New data from XRS and GRS on the Hermean surface show contents of Na [3] that are compatible with low-An pl. Natural and synthetic plagioclase spectroscopy Fig. 1 Natural (left) and synthetic (right) spectra of pl. Visible and near-infrared reflectance (VNIR) spectroscopy is the most used technique to map the surface of Solar System bodies. Pl, often considered a spectrally neutral phase, shows a clear absorption at ca. 1.25 ?m, even for very low FeO contents (Fig. 1, left); furthermore, an increase of this component, causes an increase of the depth of the absorption band, while its position moves to the IR region. We synthesised pl with different An and FeO content, in order to investigate how these parameters control the absorption band in the VNIR region. Plagioclase An90 was synthesized from oxides and carbonate at logfO2= -9; the mixture was first heated at 1600 °C for 15 minutes, quenched and then re-heated at 1400 °C for 24 hours. XRD and EPMA confirmed the presence of a crystalline phase, as well as its compositional homogeneity. As an example, a spectrum of a synthetic pl (An90) containing 0.5 wt% FeO is reported in Fig. 1, right. Conclusion and future works The synthesys of different pl will allow to create a VNIR spectra database wich will be invaluable to better constrain the composition of the crust of Solar System bodies. [1] Ohtake M. et al. (2009) Nature, 461, 236-241. [2] Cheek L.C. et al. (2012) Second Conference on the Lunar Highlands Crust, Abstract #9022. [3] Evans et al. (2013) LPSC XLIV, Abstract #2033.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
